Lecture 6: Thorax And Spine Flashcards
Prior to vertebrates, the chordates possess a rigid but flexible _________. Vertebrates arise with segmented bony elements with cartilaginous discs in between which are remnants of this structure known as the __________ __________
Notochord
Nucleus pulposus
Early tetrapods have _______ associated with each segment of the trunk. Like the earlier chordates and vertebrates, ____________ movements of the axial skeleton help with locomotion or propulsion
Ribs
Sinuous (side-to-side)
With mammalian tetrapods, there is further differentiation of the regional vertebral segments. Ribs are limited to the __________ region and there are _____ cervical vertebrae in all but a couple of taxa. There is more developed articulation of the occipital portion of the skull with the ________ and there is the odontoid process (dens) on ______. Sagittal __________ of the vertebral column is more prevalent. The sternum is _______ and the thoracic rib cage is generally _______-shaped
Thoracic 7 Atlas (C1) Axis (C2) Flexion Fused Keel
What does the term hominoid refer to?
Apes and humans
Describe the characteristics of the hominoid axial skeleton in terms of the sacrum, caudal vertebrae, and thoracic rib cage
Sacrum is expanded and fused (more segments)
Caudal vertebrae are reduced in number or absent
Conical thoracic rib cage becomes flatter/more broad
Distinct thoracic vertebral region linked to thoracic cavity
Differentiate the terms orthograde and bipedal
Orthograde = upright posture Bipedal = upright walking
What does the term hominin refer to?
Humans and their direct ancestors
Describe characteristics of the hominin axial skeleton in terms of thoracic cavity size/shape, vertebral bodies, sacral angle, and spine curvature
Expansion of thoracic cavity into barrel-shape (no longer conical)
Relative increase in size of vertebral bodies from cervical to lumbar and sacral regions (reflects weight bearing bipedal)
Prominent sacral angle and lumbar lordosis (curvature)
In general, as sacral angle increases, the lumbar convex curvature (lordosis) __________. Does a gorilla have a straighter lumbar region or more curved?
Increases
Gorillas or chimps have straighter lumbar regions and less of a sacral angle
Describe the general function of the spinal column in pronograde/quadrupeds and orthograde/bipeds
Pronograde = suspension bridge with cranium positioned out in front of spinal column
Orthograde = spine acts as an actual column with cranium positioned over it
Describe the Frankfurt plane
In the anatomical position, the skull is oriented so that the inferior margins of the orbits and the superior margin of the external acoustic meatus are horizontal
Allows for standardization of skull position to compare structures among different taxa
Describe the position of the foramen magnum as it relates to quadrupedalism vs. bipedalism
Quadrupedal species have posterior foramen magnum because spinal column extends out behind the head
Bipedal species will have more anteriorly positioned foramen magnum
Compare the thorax and lumbar region of an arboreal quadruped vs. terrestrial quadruped vs. suspensory/climber
Arboreal and terrestrial quadrupeds have narrow thorax and long lumbar region
Suspensory/climbers have broad thorax and short lumbar region
Describe bipedal features in humans including:
Foramen magnum Length of lumbar region Shape of thorax Degree of spinal curvature Degree of sacral angle Coccyx Size of vertebral bodies
Foramen magnum is positioned to hold cranium directly over spine
Relatively short lumbar region
Barrel-shaped thorax
Pronounced spinal curvature
Increased sacral angle
Reduced coccyx/no tail
Progressively larger vertebral bodies that allow weight transmission to lower limb through a columnar structure
The Australopithecines had skulls attaching more ________, a ___-shaped spine with _______ vertebrae that were not likely to be weight-bearing. They had arms that were _________ than their legs and not used for walking. They had ______-shaped pelvis with the femur angled ____. Due to these features, they were likely ___________ bipeds and mostly arboreal.
Inferiorly S Small, lighter Shorter Bowl In Facultative
Homo ergaster/erectus had a ______-shaped rib cage, lumbar _______, and probably ____ lumbar vertebrae. Because of these features, they were likely ________ terrestrial bipeds.
Barrel
Lordosis
5
Habitual
What is the junction point between the cervical and thoracic vertebrae?
Cervicothoracic junction = C7
What palpable skeletal landmark for the human back and spinal column indicates the level of T3?
Scapular spine
The inferior scapular angle is found at the level of what vertebra?
T7
Where is the “transitional vertebra” found in humans?
T12, at the level of the 12th rib
L4 is typically found at the level of what bony landmark?
Iliac crest
Describe general characteristics of cervical vertebrae in terms of size, body shape, foramen size, and characteristics of spinous processes
Smaller, rectangular bodies
Large vertebral foramen
Spinous processes are forked
Also note cervical enlargement for brachial plexus/cervical plexus and transverse foramina for passage of vertebral arteries (blood supply for midbrain)
Describe characteristics of thoracic vertebrae
Facets on transverse processes for ribs
Demi-facets on ribs articulate between the vertebrae
Somewhat longer/larger spinous processes
Larger bodies than cervical, but smaller than lumbar
Smaller vertebral foramen
Describe characteristics of lumbar vertebrae
Large bodies to support more weight
Shorter spinous processes
Shorter transverse processes
Shorter processes to accommodate lumbar lordosis
